The present invention relates to film duplicators, particularly those of the kind for making copies of a microfiche master.
The prior art discloses a variety of film duplicators. Although the details differ, such duplicators generally provide that the master be positioned and held at an exposure station, and that copy film, normally from a roll, be incrementally advanced past the exposure station for contact printing. A segment of copy film at the exposure station is typically biased into intimate contact with the master, and light is directed through the master onto the copy film to reproduce the image of the master on the copy film. After exposure, the copy film is advanced to bring a fresh segment to the exposure station.
Many prior art duplicators accumulate exposed copy film segments until the desired number of copies has been made, at which point the exposed film is processed and cut into individual segments. However, such an operating philosophy may involve substantial delays and may further make it impossible to detect malfunctioning until a whole batch has been exposed and processed.
An improvement is disclosed by the commonly owned U.S. Pat. No. 3,958,142, wherein each copy is available for processing as soon as it has been exposed. Advancement means is disposed between the film storage and the exposure station for incrementally advancing a length of copy film equal to the length of the master. Actuation of the advancing means pushes the exposed section downstream, where cutoff means immediately downstream of the exposure station severs the exposed section, making it available for processing. Separate motors are provided for operating the film advancement means, the film biasing means and the cutoff means. The stepping motors sequentially energized in the proper sequence to insure, for example, that the film is not severed until it has been advanced completely.
Although the copies represented a substantial improvement the multiple stepper motors employed by it represent a substantial expense and a source for potential failure.